Liquid formation of the dilute ultracold atomic system [1]}, [2]} is one of the most exciting topics in Bose-Einstein condensation (BEC).
The droplets have been observed in the isotropic short-range interacting system of two species of cold atoms [2]}, [4]}, [5]} as well as in the anisotropic long-range dipolar interacting system of \(^{164}\) Dy or \(^{166}\) Er atoms [6]}.
In the mixture of two component Bose atoms, the spherical droplet has been observed under the competition between the effective short range attractive interaction and the repulsive interaction due to the quantum fluctuation [7]}.
The two component BEC may be the mixture of atoms of two different elements (different atomic mass) [8]}, [9]}, [10]} or maybe the mixture of atoms with two different internal degrees of freedom of a given element [11]}, [12]}, [13]}.
In the dipolar system, the cigar-shaped droplet has been observed in the balance of attractive interaction due to the asymmetric dipolar interaction and repulsive interaction due to the quantum fluctuations. Three-body collisions limit the lifetime of the droplets. In the lower dimensions, it is expected that this lifetime can be extended because of reduced phase-space available to colliding atoms. That is why people have an interest in droplets in the lower dimension.
There are already theoretical proposals of liquid states of BEC in the lower dimensions [14]}, [15]}, [16]}, [17]}, [18]}, [19]}.
